Update on Premium IOL Evaluation

Premium IOLs require premium assessment of postoperative optical quality. Roibeárd O’hÉineacháin reports

Amyriad of new presbyopic IOLs with a range of optical qualities designed to provide the optimum compromise between depth of focus and quality of vision are now becoming available. Assessing and comparing outcomes with the lenses requires a careful examination of the image quality they produce in the eye and the patient’s postoperative visual experience, emphasises Prof Béatrice Cochener-Lamard MD, PhD.

“Quality of vision is a primary requirement for all of these socalled premium IOLs. With aspheric IOLs, you want to improve mesopic vision; with multifocality, you want to know to what extent you are affecting contrast sensitivity; with extended depth of focus (EDOF) lenses, we are all looking for social vision. But we understand today that it is still compromise we need to discuss with the patient,” she said.

With multifocal and EDOF IOLs, physicians must assess monocular and binocular UCVA and BCVA visual acuity at different distances—including the intermediate ranges of 60-80-70 cm and distances of four metres for distance acuity and 35 cm for near visual acuity. Quality of vision assessment should include subjective evaluation and objective measurement because this involves a range of vision and not a specific distance.

The subjective assessment should start with a questionnaire relating to patients’ vision-related quality of life, such as how often they require spectacles, whether they would redo the surgery, and whether they recommend it to friends. Other questions include the frequency and severity of visual complaints such as dysphotopsias, halos, and diplopia. Note should also be taken of patients’ spontaneous complaints, which are different from the reported functional symptoms.

OBJECTIVE MEASUREMENT OF OPTICAL QUALITY Objective measurements include corneal topography, which may reveal corneal irregularities or tear film, and the corneal asphericity correlated to spherical aberrations. In terms of aberrometry, the most reliable machine currently is the iTrace (Tracey Technologies), which provides measurements of the lower order aberrations connected to the refraction in addition to the higher order aberrations—including spherical aberration tilt and trefoil.

There are also halometry devices available that provide a more reliable measurement of the impact of halos on visual comfort by simulating the lighting conditions that typically give rise to the phenomenon.

“Halos can be reported in more than 40% of patients with multifocal IOLs, but among them, only 10% are really severe and spontaneously reported. EDOF IOLs also induce halos in around 20% of patients, so there is no way to get perfect quality of vision with presbyopic IOLs,” Prof Cochener-Lamard noted.

Devices are also available to measure the quality of light diffusion: the C-Quant (OCULUS), which provides an objective measurement of light scattering, and the OQAS system (Visiometrics), which provides a good assessment of opacities or disturbance of light transmission inside the eye. In addition, they allow for a static or dynamic pupillometry performance, which is important in the case of multifocal IOLs because they are pupil-size dependent. EDOF lenses, on the other hand, are not dependent on pupil size when their concept is based on asphericity modulation.

Prof Cochener-Lamard noted that classical machines from Vector Vision provide useful measurements of contrast mesopic and photopic conditions with or without glare. There are also new ophthalmic assessment platforms such as the EyeVis Pod CSV 1000 (Vector Vision) that allow the objective measurement of quality of vision and provide contrast sensitivity and defocus curve in a more dynamic and user-friendly way.

“The beauty of these new platforms is the very automatic way you can get the defocus curve from -4.0 to +2.0 D. We are all looking for a continuity of this kind of dome-shaped curve as opposed to the two peaks we associate with a bifocal lens,” she said.

Last but not least, Prof Cochener-Lamard emphasised the importance of the ocular surface and the tear film because of the impact they can have on both preoperative and postoperative measurement. There is also an increase in tear evaporation with the aging process with MGD present about 50% at the time of cataract. The refractive power of the tear film is demonstrated by the fact the difference in refraction between two blinks will increase and induce visual fluctuation in case of OSD.

However, expensive equipment is not necessary or mandatory to check for signs of ocular surface disease. Just one drop of fluorescein and careful examination of the eyelids to check for meibomian gland dysfunction is adequate and brings so much information, she advised.

“The outcome evaluation of advanced IOL implantation goes far beyond visual acuity. Achieving 20/20 is not enough. Visual quality is even more crucial than it is with corneal refractive surgery—presbyopic surgery is much more demanding. There are tools we can use to quantify the quality of vision required nowadays to evaluate outcomes in refractive IOLs to demonstrate the additional value of new optics and compare one concept to another,” Prof Cochener-Lamard concluded.

“Quality of vision is a primary requirement for all of these socalled premium IOLs.”

This presentation occurred at the 39th Congress of the ESCRS in Amsterdam.

Béatrice Cochener-Lamard MD, PhD, is Professor and Head of the Department of Ophthalmology at the University Hospital of Brest, France. beatrice.cochener@univ-brest.fr